"It takes time to learn the ropes" means it takes time to learn and understand how to do a skill or task. "The ropes" is just another way of saying "how things are done" basically.
Other uses include: "show someone the ropes" - to show someone else how a task is done and "know the ropes" - to understand how things are done.
"It takes time to learn the ropes at a new job." = "It takes time to learn how to do things at a new job."
"I'll show you the ropes so you can do it yourself later." = "I'll teach you how to do this task so you can do it yourself later."
"I've been here a long time so I know the ropes of this job really well, ask me anything." = "I've been here a long time so I know how to do everything around here, ask me anything."